a. Field of the Invention
This invention relates to methods for preparing polyester polymers from glycol phthalate prepolymers.
B. Description of the Prior Art
It is known to use germanium dioxide as a catalyst in a polycondensation reaction to produce polyesters. The germanium dioxide is sometimes added to the reaction mixture with a glycol, such as ethylene glycol. Unfortunately, crystalline germanium dioxide has a very low solubility in the glycol, resulting in undissolved catalyst particles which remain in the polymer. The undissolved catalyst particles tend to result in undersirable physical characteristics in fibers made from the polymer.
It is known to use other catalysts, such as antimony glycoloxide, in the preparation of polyethylene terephthalate and other polymers. One of the disadvantages of these catalysts is that, unless excessive amounts are used, much longer reaction times are required.
In the process of the present invention catalyst particles do not present a problem and reaction time is substantially reduced.